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1. Field of the Invention
The present invention relates to heavy equipment, and more particularly to heavy lifting equipment that is used in commercial applications for lifting very heavy multi-ton objects that can weigh as much as several thousand tons. Even more particularly, the present invention relates to an improved heavy lifting apparatus that includes a pair of spaced apart trusses, each formed of a pair of booms, each pair being pinned at an upper boom end portion and load transfer carriages provided at the lower ends of the pair of booms, the carriages being connected with a tensile element (e.g., winch cable) that can be wound upon sheaves to increase the mechanical advantage. One of the carriages has a winch that pulls the cable and the two carriages together increasing the angle of inclination of each boom during a lift, a horizontal lifting beam being suspended below the booms for rigging the package to the horizontal beam.
2. General Background of the Invention
In the construction industry and at industrial plants, there is great expense associated with the lifting of very large objects such as chemical process vessels, large pieces of equipment, pre-fabricated buildings and the like. Such objects are typically lifted with one or more very large and expensive devices such as high capacity lifting booms or cranes.
These cranes must be brought into the facility and assembled on site before use when very large lifts are contemplated. This is a very time consuming and expensive operation costing millions of dollars, even for one lift in some cases where the load is very large (e.g., several thousand tons). Scheduling of large equipment can be critical, due to the limited number of very large capacity cranes world-wide and the time restraints and deadlines associated with plant expansions, turnarounds and renovations.
Some of the problems with the lifting of very large objects is the mobilization cost, the complex rigging that must be accomplished timely, and demobilization once the lift is completed.
Huge counterweights are required to equally distribute load, especially if soil conditions are less than perfect. With a crane, ground pressures can be 1000-5000 pounds per square foot. A foundation failure is one of the greatest concerns in any land heavy lift in the Gulf Coast area of the United States. With the present invention, soil bearing pressures are distributed to four carriages. Each carriage then further distributes the load in a balanced manner so that soil bearing pressure might be 100-500 pounds per square foot.
When moving the load (once lifted) over the ground, the present invention is far more stable than a crane that is walking a load. Another problem with crane lifts is that of a rotation or shifting of the object being lifted so that it hits the crane. During a lift, a crane boom is under such stress, that catastrophic failure can result when the object being lifted even lightly hits the crane.
The present invention can be positioned inside buildings without structural modifications that are required when an overhead crane is installed. The only constraint with the present invention is that the apparatus fit inside the building once assembled.
Cranes can also fail if the object being lifted moves (e.g., with wind load) out away from the center of the hook.
The present invention provides an improved method and apparatus for lifting multi-ton packages such as chemical vessels, pre-fabricated structures, equipment packages and the like. This invention requires no counterweights, which can be costly to transport and assemble, because it operates using leverage against itself. Power requirements are reduced using this invention, as the power supply is the horizontal extendable member which carries only the horizontal component of boom load. Ground pressure, a significant problem associated with heavy loads, can be reduced by an order of magnitude by dividing the weight onto four evenly loaded carriages instead of eccentrically loading one crane matrix.
The method of the present invention first provides for the supporting of a first pair of booms from a first pair of carriages or vehicles, wherein the lower end portion of a first boom is pinned to a first carriage, and the lower end portion of the second boom is pinned to the second carriage.
A second pair of booms is supported from a second pair of carriages, wherein the lower end portion of a third boom is pinned to a third carriage and the lower end portion of a fourth boom is pinned to a fourth carriage. Each pair of booms and its carriages defines a generally triangularly shaped variable dimension truss.
The method contemplates pinning the upper end portion of the first and second booms together. The method also contemplates pinning the upper end portion of the third and fourth booms together. These pairs of booms support rigging for lifting the desired multi-ton package, vessel, structure, etc. The booms can be elevated to an erect position by pulling the carriages (on a given track) together. Alternatively, the booms can be erected to their working height and working positions by lifting each respective pair of booms with two (2) land cranes. Then, horizontal slings or cables can connect the pair of carriages on a given railway or like base together from carriage to carriage. This will be feasible in many cases because numerous large construction yards have an inventory of cranes with long booms (for example, 150 feet-250 feet) and lift capacities of about 50-100 tons or more. Such land cranes can erect the four booms in lieu of the horizontal cable and winch that can also be used to pull the carriages on a given track together.
The rigging can include a lifting beam that is generally horizontally positioned and suspended from the upper end portions of the respective pairs of booms, and preferably from the pinned connections of the two variable dimension trusses.
A package is lifted with rigging (eg. traveling blocks, slings, fast line) that depends from the lifting beam when a tensile member (eg. cable) is tightened between the first and second carriages. Likewise, the lifting contemplates a tightening of a second cable that links the third and fourth carriages.
The apparatus of the present invention includes a plurality of carriages that define a structural base for supporting the load to be lifted.
Each truss supported by the plurality of carriages defines a load transfer between the carriages and the multi-ton packages to be lifted.
The trusses include the multiple booms extending respectively from the plurality of carriages and cables that extend in between the pairs of carriages during use.
A first pair of carriages supports a first pair of booms with upper end portions that are pinned together. A second pair of carriages supports the second pair of booms with upper end portions that are pinned together at pinned connections. A lifting beam is supported below the pinned connections.
A first extensible, powered lifting cable connects the first pair of carriages for pulling the carriages together so that the first pair of lifting booms increase in inclination during lifting, thus raising the apex of the first pair of booms and lifting the beam and the object to be lifted.
A second extensible, powered lifting cable connects the second pair of carriages for pulling the carriages together so that the second pair of lifting booms increase in inclination during lifting, thus raising the apex of the second pair of booms and lifting the beam and the object to be lifted.